Radiation therapy can help cure many children facing Hodgkin lymphoma and other cancers. When the radiation is delivered to a girl’s chest, however, it can lead to a marked increase in breast cancer risk later in life.

In a new study, SmitaBhatia found that women who received even low doses of radiation therapy to their chests as children have an increased breast cancer risk later in life.

A recent multi-institutional study that included City of Hope’s SmitaBhatia, M.D., M.P.H., the Ruth Ziegler Chair in Population Sciences, examined the long-term effects of chest radiation on female survivors of childhood cancers, primarily Hodgkin lymphoma. The researchers wanted to determine whether more current therapies using less radiation could reduce the breast cancer risk, and if the amount of area exposed was a factor.

Past research has shown that standard doses of radiation therapy to the chest increase breast cancer risk, with incidence rates among these women ranging from 5 percent to 14 percent by age 40.

For the current chest radiation study, lead author ChayaMoskowitz, Ph.D., of Memorial Sloan Kettering Cancer Center in New York, and the research team looked at more than 1,200 women who received various amounts of radiation in treatment of childhood cancers. They found that even women who received lower amounts of radiation as children still were much more likely to develop breast cancer than the average woman, with as many as 30 percent developing breast cancer by age 50.

The scientists also examined whether the amount of tissue exposed to those lower levels of radiation made a difference. While less exposure meant less risk, the risk was still higher than the average woman’s. The researchers found a significant rise in breast cancer risk for women as the amount of tissue exposure increased.

Further, the study compared — possibly for the first time — these women’s risk of breast cancer with that of women with mutations in their BRCA1 genes. That’s the mutation that prompted Angelina Jolie to undergo surgeryto remove her breasts to prevent breast cancer, known as a prophylactic surgery. The scientists found that the survivor’s risk by age 50 was nearly the same as if they had BRCA1 mutations.

“Our findings strongly suggest that these women who received radiation therapy to their chests as children should receive more rigorous screening for breast cancer beginning at a younger age,” Bhatia said.

The researchers hope to expand the study in the future to get more data on survivors of diseases other than Hodgkin lymphoma. The added evidence may push doctors to increase their monitoring of breast cancer patients, and encourage patients to make lifestyle changes that could help counter their increased risk.

Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under grant numbers U24CA55727, R01CA136783, K05CA160724, R01CA134722, U01CA83178, R01CA097397, and R01CA129639. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.